Return of the Otter
Native populations of Eurasian otters compete with humans for resources, in particular Atlantic salmon, which is now on Norway’s red list of threatened species. We spoke to Dr Marius Kambestad and Dr Rose Keller about their work in investigating the nature of the humanotter conflict, which could then lead to more effective strategies to manage otter populations.
The Eurasian otter was hunted quite extensively in Norway for much of the twentieth century, to a point where it was almost entirely extirpated from the whole country, before it became a nationally protected species in 1982. The otter population has since recovered to an extent in some coastal regions of Norway, but this has also led to conflicts with local people where humans and otters compete for the same resources, in particular wild Atlantic salmon. “The biggest source of conflict between humans and otters in Norway is competition for wild salmon,” says Marius Kambestad, a researcher in the Climate and Environment division at the Norwegian Research Institute (NORCE). Wild salmon is now on Norway’s red list of threatened species, entering it in the same year that otters went off it. “Otters are now of least concern, we think they are mostly doing fine, but salmon aren’t,” continues Kambestad.
RePress project
This has led to calls from local stakeholders to control the otter population and prevent them from preying on salmon. As part of his work in the RePress project, an initiative funded by the Research Council of Norway, Kambestad is seeking to build a deeper picture of how otters prey on salmon in the Sunnmøre region of Western Norway, which could then inform
future, non-lethal management strategies. “We tag salmon with radio tags, so we can track them with antennae along a river and gather data,” he outlines. “For example, if we tag 50 salmon in a river we can see where they are and determine their fate; did they survive long enough to spawn? Does sex and size matter in terms of survival prospects? Did the time of year matter, the water level? We can investigate these types of questions by tagging the fish.”
The project’s agenda also includes tagging otters, with the aim of understanding their hunting behaviour. A GPS tag fitted with an accelerometer will be attached to a number of otters, from which the research team hopes to pinpoint the locations in rivers where they choose to hunt salmon. “We want to find the hot-spots, and we will test various otter deterrents there,” says Kambestad. Salmon are
at great risk of being eaten at almost all stages of their lives, but as adults it’s when they enter rivers to spawn that predation really picks up.
“Salmon need to spend a few months in a river to find their spawning habitat, compete for it, then lay their eggs. But this is a very vulnerable time with otters back, especially in smaller rivers,” continues Kambestad. “This is the natural situation, but over the last few decades Norwegian salmon have not really faced many predators in this stage of their lives.”
This may mean that some of the fish lack effective evasion strategies, a topic that Kambestad plans to look into in the project.
Inter-breeding between wild and farmed salmon is one of the major reasons why salmon is now an endangered species in Norway, says Kambestad. “Farmed fish escape and inter-breed with local fish, while they also proliferate salmon lice,” he outlines. Genetic studies show significant inter-breeding in salmon populations in a high proportion of Norwegian rivers, and these fish tend to behave differently. “Farmed salmon are bred to be risk-takers. They are bred to grow fast and get food as quickly as possible,” says Kambestad.
“Juveniles with these genes in nature are more liable to get eaten by predators, now our data from otter predation studies will allow us to test whether this is true for adults as well.”
Managing otters
The wider context here is the goal of helping the Atlantic salmon recover, without resorting to culling their predators. Management measures must command public support if they are to be fully effective, and in general the Norwegian population is willing to take an active role in managing the natural world, as shown by recent international research on wildlife value orientations. “Norway’s samples stood out, with people more strongly oriented towards seeing themselves as taking an active role in nature, so determining what species belong where,” says Rose Keller, a researcher at the Norwegian Institute for Nature Research (NINA) who is also working on RePress. As part of her work in the project, Dr Keller is looking to assess public attitudes towards otters. “We launched a national survey to look at people’s perspectives,” she outlines.
The aim is to understand people’s relationship with their local environment and gauge their views on the extent to which humans should try to manage or control the natural world. These attitudes are underpinned by different values and belief structures, with research showing that age is an important factor. “We found that older people were more likely to support otter management measures than younger people,” explains Dr Keller. Understanding these attitudes is central to building support for management strategies, with some people in the region very dissatisfied with what they perceive as current non-management of otters, to a point where they have started illegally trapping them themselves. “There are strong calls for a management strategy. Many people don’t see letting nature take its course as a viable strategy,” says Kambestad.
“Salmon need to spend a few months in a river to find their spawning habitat, compete for it, then lay their eggs. But this is a very vulnerable time with otters back.”
This survey was conducted on both the national and regional level, and while there was broad agreement that otters attacking wild salmon could be a problem, differences emerged in terms of what action should be taken. The population of Sunnmøre generally supported otter control, compared to more diverse attitudes about otters (re)inhabiting rivers in Norway, but Dr Keller still expects that opinions on otters will vary widely in the region. “We expect that certain local stakeholders will probably be quite pro-otter (e.g., less active management and anti-private culling), others very much less so (pro-management and private/legal culling), and there will be a range of opinions inbetween (promanagement, not culling),” she says.
A fieldwork campaign will be conducted to gain deeper insights, in which local people will be asked to walk along a river then answer a series of questions. “We will be asking individuals to describe what seems to be a natural functioning system about their local area, and what it would be like with - or without - otters,” continues Dr Keller. Management options for otters include invasive acoustic or visual features in the local landscape, now Dr Keller aims to assess public opinion on these different nonlethal management strategies. “Local voluntary participants will answer questions and we will track their physiological response to the same management measures as the otters,” she outlines. “We want to see how they respond and if these management measures actually could result in unintended consequences related to social acceptance of otter management.”
Researchers in the project plan to hold interviews with local managers to gather more data, while regular group meetings are being held to provide updates on the project’s findings and guide its ongoing development. This active engagement with local communities will help build support for the otter management strategies under development. “We’re going to test deterrents in the river, three or four different ways of affecting otters so that they don’t kill as many salmon in these hot spots, where the populations are quite vulnerable,” outlines Kambestad. “If we find one or two that work, that could really make a difference.”
RePress
Return of the otter: Aggravation of humanwildlife conflict and potential for mitigation strategies for coastal areas under pressure
Project Objectives
The project investigates the human-wildlife conflict arising as the once extirpated Eurasian otter returns to salmon rivers along the Norwegian coast. We will quantify effects of otter predation on vulnerable salmon stocks and investigate otter behavior around predation hot spots. We will also evaluate stakeholder perspectives, reveal preferences for management strategies, and test non-lethal control measures.
Project Funding
Fully funded by The Norwegian Research Council. Industry partner Hofseth Aqua AS has also made a small in-kind contribution.
Project Partners
Project Leader: Norwegian Research Centre (NORCE), Norwegian Institute for Nature Research, University of South-Eastern Norway, Cornell University (US), UK Centre for Ecology & Hydrology, Hofseth Aqua AS (industry partner), Lakseelvene på Sunnmøre, Bergen Aquarium
Contact Details
Project Coordinator, Dr Marius Kambestad, Researcher Nygårdsgaten 112, 5008 Bergen, Norway
NORCE
T: +47 452 06 875
E: maka@norceresearch.no
W: www.norceresearch.no
Dr Marius Kambestad is an ecologist mainly focusing on freshwater ecology and conservation of salmonids. His work revolves around river restoration, predator-prey dynamics, population monitoring, and the effects of human interventions such as habitat alterations, aquaculture, and harvesting. Methods commonly used in his projects include fish telemetry, electric fishing, snorkeling surveys, and habitat mapping.
Dr Rose Keller is a research scientist for the Norwegian Institute for Nature Research: Nature, Society and Areal Department. She focuses on nature-based tourism in protected areas and has a background in research in academia and as a social scientist in the U.S National Park Service (Alaska).
